As Indigo and Violet come after Blue in the rainbow, they should therefore exist and be the hottest stars in the Universe but we have no stars of that colour. The hottest stars are the blue stars and an example of this is Spica in the constellation of Virgo.

Although you can spot many colors of stars in the night sky, purple and green stars aren't seen because of the way humans perceive visible light.

Violet stars are of two temperature ranges: those whose Planckian peak wavelength lies between 380 and 450 nm, or 6700-7900 K temperature and those above the violet range in the ultraviolet that appear violet to blue in color. For example, A spectral type stars range in temperature from 7600 to 11,500 K.